Re: [Qemu-devel] [PATCH v2 10/11] trace-state: [stderr] add support for dynamically enabling/disabling events

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Apr 6, 2011 at 7:35 PM, Lluís <xscript@gmx.net> wrote:
> This includes all the control interfaces already provided by the "simple"
> backend (i.e., command line, programmatic and monitor).
>
> Signed-off-by: Fabien Chouteau <chouteau@adacore.com>
> Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
> ---
>  Makefile.objs     |    8 +++++++-
>  configure         |    3 +++
>  docs/tracing.txt  |    6 ++----
>  hmp-commands.hx   |   10 ++++++++--
>  monitor.c         |    8 +++++++-
>  qemu-config.c     |    7 ++++---
>  qemu-options.hx   |    8 +++++++-
>  scripts/tracetool |   33 ++++++++++++++++++++++++++++-----
>  stderrtrace.c     |   24 ++++++++++++++++++++++++
>  stderrtrace.h     |   14 ++++++++++++++
>  vl.c              |   11 +++++++++--
>  11 files changed, 113 insertions(+), 19 deletions(-)
>  create mode 100644 stderrtrace.c
>  create mode 100644 stderrtrace.h

I feel that the monitor commands for the simple backend were a
mistake.  Simple trace is used during development, not production, so
being able to toggle trace events at runtime is probably not worth the
extra user interfaces we've added.  But when the simple backend was
written we thought it would be used in production and planned for
libvirt interfaces and all ;).

Let's not go down that road for the stderr backend which is very
useful today at a tiny cost in code size.

For tracing use cases that require performance or runtime
enabling/disabling trace events, just use the simple, ust, or dtrace
backends.

Please drop this patch.

Stefan